Solid state electronic devices are typically encapsulated in plastic via transfer molding. Encapsulation protects the device from environmental and mechanical damage and electrically isolates the device. There are many desired technical features of encapsulant compositions. Encapsulation of wire-bonded devices requires low viscosity encapsulant injection, followed by rapid cure and hot ejection. In order to avoid damaging the solid state device, the encapsulant must not shrink excessively on curing. The encapsulated device must subsequently withstand the rigor of solder assembly onto a circuit card. The encapsulant must also be self-extinguishing in the event of a heat-producing malfunction of the circuit. And the encapsulant must adhere strongly to copper leadframes.
Although current epoxy-based encapsulation compositions perform adequately in many applications, there is a desire for compositions that provide improved adhesion to copper, reduced shrinkage, reduced moisture absorption, and reduced coefficients of thermal expansion.